256 
splendidly exposed, the whole crest of the mountain consist- 
ing of such rocks of a total thickness of several hundred meters, 
whilst the red sandstone at the south western side of the foot 
of the mountain stands out with its usual characteristics as 
mentioned on p. 254. 
On ascending the Iganek Mountain from the west, the first 
traces of the contact metamorphism already appear at an alti- 
tude of about 50 meters, the red colour of the sandstone dis- 
appearing, and the beds assuming a white or gray colour. The 
alteration is more intense higher up the mountain. The beds 
which consist of relatively pure quartz-sandstone are white and 
quartzilic, the impure beds appearing like dark gray, fine-grained 
seams. On microscopic examination these dark gray beds show 
the following peculiarities: the quartz grains have retained their 
rounded contours, but the cement has been re-crystallized to 
an aggregate of felspar and quartz grains, through which a 
number of other minerals are disseminated: granules of a col- 
ourless pyroxene, scales of biotite, minute specks of black iron 
ore, and groups of hornblende needles. These are in some 
cases blue and crocidolite-like, in others they resemble ac- 
tinolite. 
In the upper part of the mountain the operations of the 
contact metamorphism reach their maximum. ‘The rocks are 
hornfels and while quartzite, the beds of the first mentioned 
being exeedingly numerous, varying in thickness from a few 
centimeters to about ten meters. The fissures in the rock are 
covered by crystals of garnet, epidote, actinolite, fluorite, and 
sometimes graphite. The hornfels beds are most frequently 
black or dark gray, but gray and pale green beds may be found 
too. All of them are of a massive not schistose structure, their |. 
size of grain being extremely small, irrespective of the large 
scales of black mica which are to be found in many of them. 
A large part of these hornfels rocks are no doubt. alteration 
products of the diabases and other igneous rocks occurring as 
